This invention relates generally to systems for diagnosing and treating medical conditions using multiple electrode catheters and, more particularly, to systems and methods of interfacing both personnel and equipment with such catheters.
Multiple electrode catheters are widely used in diagnosing and treating a variety of medical conditions. Today, physicians use such catheters to examine the propagation of electrical impulses in heart tissue to locate aberrant conductive pathways. The techniques used to analyze these pathways, commonly called "mapping," identify regions in the heart tissue, called foci, which can be ablated to treat the arrhythmia.
One form of conventional cardiac tissue mapping technique uses a multiple electrode catheter positioned in contact with epicardial heart tissue to obtain multiple electrograms. The physician stimulates myocardial tissue by introducing pacing signals and visually observes the morphologies of the electrograms recorded during pacing. The physician visually compares the patterns of paced electrograms to those previously recorded during an arrhythmia episode to locate tissue regions appropriate for ablation. These conventional mapping techniques require invasive open heart surgical techniques to position the electrodes on the epicardial surface of the heart.
Another form of conventional cardiac tissue mapping technique, called pace mapping, uses a roving electrode in a heart chamber for pacing the heart at various endocardial locations. In searching for the VT foci, the physician must visually compare all paced electrocardiograms (recorded by twelve lead body surface electrocardiograms (ECG's)) to those previously recorded during an induced VT. The physician must constantly relocate the roving electrode to a new location to systematically map the endocardium.
In still another form of mapping called "impedance mapping," the resistivity of cardiac tissue is measured using an injected current. Infarcted cardiac tissue is detected by virtue of the lower electrical resistivity such tissue displays relative to healthy or normal tissue.
Multiple electrode catheters greatly increase the effectiveness of these various procedures. Such catheters make it possible to simultaneously obtain data from several locations within the heart or other organ using a single catheter. However, as the catheters become more sophisticated, it becomes more and more difficult to process and interpret the resulting data in a meaningful way. Known cardiac mapping and pacing catheters contain as many as sixty-four individual electrodes, each of which can be used for both mapping and pacing. It is reasonable to believe that further advances will enable still more electrodes to be used. Along with the flexibility, resolution and utility provided by such catheters comes the need to process and interpret the resulting data in an efficient, organized manner.
Various approaches have heretofore been taken in processing and interpreting data acquired through multiple electrode catheters. In one prior approach, the various waveforms acquired by the individual electrodes were displayed on a screen. The medical personnel mentally integrated the heart activity and position data as displayed on the recorder and fluoroscopy screens in order to assess the health of the underlying tissue. This approach required a considerable degree of skill and experience on the part of the attending medical personnel. Furthermore, information regarding the relative location of an ablation catheter with respect to the multiple electrodes was not readily available. More significantly, the system became impractical and unwieldy as the number of electrodes increased.
In another prior approach, information acquired from a number of sequential locations of a roving electrode was digitally sampled and combined to construct a model "surface" that was displayed on a screen and that visually represented the tissue under consideration. Although much easier to interpret than the prior approach that required mental integration of various inputs, this system, too, provided an unrealistic representation that required skill and experience to use effectively. Furthermore, the surface was difficult to generate as it required that a roving electrode be moved over the surface of the heart to reconstruct its geometry point by point. To get reasonable accuracy, a high, sometimes impractical, number of points was necessary.
Various other data acquisition systems have been developed for processing data acquired during cardiac mapping and pacing procedures. Typically, such systems record data through multiple recording inputs and process the data to assist the physician in making a diagnosis and rendering treatment. Some systems also include circuitry for generating pacing pulses that can be applied to the heart. Although effective in their intended application, known data acquisition systems become limited in their capabilities as more and more data are provided by more and more sophisticated catheters. Nor do existing systems automatically and continuously monitor the electrodes to warn the physician in the event of a malfunction in the catheter. As catheters become more sophisticated, the number of possible failure modes unavoidably increases. In a multiple electrode system, it is possible for some of the electrodes to be open or shorted.
Many known data acquisition systems only support input from up to twenty-four electrodes and are not directly useful with catheters containing more than twenty-four electrodes. Because data acquisition systems are larger, more complicated and more expensive than the cardiac catheters used in mapping and pacing, it is impractical to redesign a data acquisition system each time an advance is made in the catheter art. Nor is it economically sound for health care providers to retire still serviceable existing systems in favor of the latest model each time a new catheter is introduced. As advances are made in the catheter art, a need develops for adapting the new catheter to use with existing data acquisition systems.
To be of maximum benefit to medical personnel, it is desirable to display information in such a way that it can be easily related by the physician to information provided by existing visualization or imaging systems, such as a fluoroscopic system. Visually based systems, which enable such personnel to "see" what is happening, offer a viable means of presenting large amounts of data in a form that can be readily grasped and understood. Graphical user interfaces are one means by which such a goal can be achieved.